Guanghao Zhang created HBASE-17178:
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Summary: Add region balance throttling
Key: HBASE-17178
URL: https://issues.apache.org/jira/browse/HBASE-17178
Project: HBase
Issue Type: Improvement
Components: Balancer
Reporter: Guanghao Zhang
Our online cluster serves dozens of tables and different tables serve for
different services. If the balancer moves too many regions in the same time,
it will decrease the availability for some table or some services. So we add
region balance throttling on our online serve cluster.
We introduce a new config hbase.balancer.max.balancing.regions, which means the
max number of regions in transition when balancing.
If we config this to 1 and a table have 100 regions, then the table will have
99 regions available at any time. It helps a lot for our use case and it has
been running a long time
our production cluster.
But for some use case, we need the balancer run faster. If a cluster has 100
regionservers, then it add 50 new regionservers for peak requests. Then it need
balancer run as soon as
possible and let the cluster reach a balance state soon. Our idea is compute
max number of regions in transition by the max balancing time and the average
time of region in transition.
Then the balancer use the computed value to throttling.
Examples for understanding.
A cluster has 100 regionservers, each regionserver has 200 regions and the
average time of region in transition is 1 seconds, we config the max balancing
time is 10 * 60 seconds.
Case 1. One regionserver crash, the cluster at most need balance 200 regions.
Then 200 / (10 * 60s / 1s) < 1, it means the max number of regions in
transition is 1 when balancing. Then the balancer can move region one by one
and the cluster will have high availability when balancing.
Case 2. Add other 100 regionservers, the cluster at most need balance 10000
regions. Then 10000 / (10 * 60s / 1s) = 16.7, it means the max number of
regions in transition is 17 when balancing. Then the cluster can reach a
balance state within the max balancing time.
Any suggestions are welcomed.
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